Scala community.
Currently I'm trying to implement custom model/single parameter validation using cats Validated
Monad. But, after removal of Cartesian product since 1.0 I'm unable to use (v1 |@| v2) map (f) and unable to compile my code:
import cats.Semigroupal
import cats.data.Validated.{Invalid, Valid}
import cats.data.{ValidatedNel, _}
import cats.implicits._
import cats.instances.all._
case class FieldErrorInfo(name: String, error: String)
type FieldName = String
type ValidationResult[A] = ValidatedNel[FieldErrorInfo, A]
trait SingleFieldValidationRule[U] extends ((U, FieldName) => ValidationResult[U])
trait ModelValidationRule[M] extends (M => ValidationResult[M])
object ValidateNameRule extends SingleFieldValidationRule[String] {
override def apply(v1: String, name: String): ValidationResult[String] = {
if (v1.contains("cats"))
v1.validNel
else
FieldErrorInfo(name, "Some Error").invalidNel
}
}
object ValidateQuantityRule extends SingleFieldValidationRule[Int] {
override def apply(v1: Int, name: String): ValidationResult[Int] =
if (v1 > 0)
v1.validNel
else FieldErrorInfo(name, "Some Error").invalidNel
}
case class SampleModel(name: String, quantity: Int)
object ValidateSampleModel extends ModelValidationRule[SampleModel] {
override def apply(v1: SampleModel): ValidationResult[SampleModel] = {
val stage1: ValidatedNel[FieldErrorInfo, String] = ValidateNameRule(v1.name, "name")
val stage2: ValidatedNel[FieldErrorInfo, Int] = ValidateQuantityRule(v1.quantity, "quantity")
implicit val sga: Semigroupal[NonEmptyList] = new Semigroupal[NonEmptyList] {
override def product[A, B](fa: NonEmptyList[A], fb: NonEmptyList[B]): NonEmptyList[(A, B)] = fa.flatMap(a => fb.map(b => a -> b))
}
(stage1, stage2).mapN(SampleModel)
}
}
Compiler says, that
Error:(43, 23) value mapN is not a member of (cats.data.ValidatedNel[FieldErrorInfo,String], cats.data.ValidatedNel[FieldErrorInfo,Int])
(stage1, stage2).mapN(SampleModel)
^
Point me please how to use new Applicative syntax or what I did wrong...(forgot to create/import some implicits)
Values stage1
and stage2
must have type ValidationResult[_]
.
In this case implicit for mapN
should work.
object ValidateSampleModel extends ModelValidationRule[SampleModel] {
override def apply(v1: SampleModel): ValidationResult[SampleModel] = {
val stage1: ValidationResult[String] = ValidateNameRule(v1.name, "name")
val stage2: ValidationResult[Int] = ValidateQuantityRule(v1.quantity, "quantity")
(stage1, stage2).mapN(SampleModel)
}
}